This invention relates to a granulator and especially to an improved sheet feeding apparatus associated therewith so as to accomplish improved operations as will hereinafter be indicated. In order to reprocess waste or off-specification plastic sheet material, it is known to granulate such for subsequent ease in transporting, melting and the like. In order to accomplish such, it is necessary that the sheet material be positively fed to the granulation chamber, preferably in a continuous manner and trouble free.
In processing sheet material such as the edge trim from extruded plastic sheet, it is normal to twist or otherwise bunch several such trim ribbons together into a longitudinally extending rope which is thereafter directed to the nip of a pair of opposed driven feed rolls. Feed rolls of this general type are known and include those described in U.S. Pat. No. 4,028,779 issued June 14, 1978 and U.S. Pat. No. 4,176,796 issued Dec. 4, 1979. Both of such aforementioned patents are directed to inventions other than the construction of such feed rolls and the means for driving such per se but disclose roll constructions which can be utilized to feed such roped sheet. Such edge trim is normally about 3 inches wide as for a 3 or 4 foot wide sheet; however, various other widths can be utilized. Various thicknesses may be assumed dependent on that of the sheet material extruded. Generally, however, the thicknesses of material which the present invention deals with are on the order of several thousandths of an inch thick, i.e. from about 0.001 inches to about 0.05 inches. Such films are not self-supporting and accordingly present considerable problem in feeding and thus require some mechanism of grouping or plying multiple ribbons together as in forming the above-described roping. Thus, extremely thin, flexible and generally non-self-supporting film ribbons can generally be satisfactorily fed to granulation equipment by such above-discussed feed roll constructions since the necessary thickness to insure proper feed is achieved by such twisting or roping of the various sheets which individually would otherwise present a difficult feed task. However, since the length of such individual ribbons is generally not equal, one or more of such ribbons often play out in the overall rope construction at various positions along the length of the rope and accordingly an inadequate sheet thickness, e.g. a single sheet of material, is occasionally presented to the feed rolls which can and often does present a feed problem, i.e. slippage or roll wrap. In either event, the feed is undesirably stopped and thus requires appropriate operator attention.
It is accordingly an object of the present invention to provide a feed roll apparatus of improved construction so as to avoid the aforementioned drawbacks. These and other objects of the invention are accomplished by the provision of a sheet material feed drive for operation with a granulator having a rotor mounted for rotation about an axis within a granulation chamber. Such feeding device comprises first and second longitudinally oriented, generally cylindrical feed rolls coaxially mounted with respect to each other so as to form a longitudinally directed nip for receipt of a minimum thickness of at least a single material sheet therebetween and a maximum thickness of a plurality of said sheets. The rolls each include a plurality of radial grooves inwardly extending a distance slightly greater than said maximum material thickness and longitudinally spaced from each other so as to form a plurality of spaced ridges adjacent said grooves and wherein said rolls are longitudinally positioned with respect to each other so that the ridges of one of the rolls and the grooves of the other rolls and vice versa are aligned for respective interdigitation. Such roll construction forces sheet material fed to the nip thereof into a sinuous cross-sectional configuration and imparts different frictional surface velocities to opposite surfaces thereof.